Dana continues the discussion of fluorescent pigments with green, yellow-green and yellow fluorescent pigments and a few hypotheses concerning their function.

In Part 1 of this series, we began our review of fluorescent
pigments and also discussed the concepts of fluorescence
excitation and emission, Stokes shift, photoconversion and so
on. A review of that article is recommended if you are
unfamiliar with any of these terms. This time, our discussion
continues with green, yellow-green and yellow fluorescent
pigments and a few hypotheses concerning their function.
We’ll also see a couple of cases where light energy of
specific bandwidths has induced coloration changes.

This Hawaiian soft coral (Sinularia densa) demonstrates green fluorescence.
The reddish coloration is that of zooxanthellae or algal fluorescence.

Green fluorescence is perhaps the most common of any seen in
aquaria. Well over half of the 70 or so known fluorescent
pigments spanning 9 color categories can be described as
‘greenish.’ Fluorescence of green fluorescent
proteins (GFPs) can also combine with other
‘glowing’ pigments to form any number of
colors.

Table 4 lists
the fluorescent proteins by emission maxima as described in
various works:

Table 4: Fluorescent Proteins by Emission Maxima

Pigment

Emission

2

3

Excitation

2

Found in:

Reference

P-510

510

479

*

*

*

Montastraea annularis

Mazel, 1995

P-510

510

*

*

*

*

Ricordea florida

Mazel, 1995

P-510

510

*

*

498

*

Renilla muelleri (sea pansy)

Labas et al., 2002

P-510

510

*

*

490

420

Heteractis magnifica

Tu et al., 2003

P-510

510

*

*

440

*

Montastraea cavernosa

Mazel et al., 2003

P-510-520

510-520

*

*

440

*

Montastraea faveolata

Lesser et al., 2000

P-510-520

510-520

*

*

440

*

Montastraea cavernosa

Lesser et al., 2000

P-510-623

510-623

*

*

*

*

Montastraea cavernosa @ 40m

Vermeij et al., 2002

P-511

511

*

*

*

*

Plesiastrea verispora (green morph)

Salih et al., 2004

P-512

512

*

*

503

*

Discosoma sp. 3

Labas et al., 2002

P-512

512

*

*

*

*

Plesiastrea verispora (blue morph)

Salih et al., 2004

P-512

512

*

*

*

*

Plesiastrea verispora (green morph)

Salih et al., 2004

P-513

513

545

490

*

*

Agaricia sp.

Mazel, 1995

P-513

513

*

*

*

*

Ricordea florida

Mazel, 1995

P-514

514

490

*

501

480

Acropora aspera

Papina et al., 2002

P-514

514

*

*

*

*

Montastraea cavernosa

Kelmanson & Matz, 2003

P-515

515

*

*

*

*

Mycetophyllia lamarckiana

Mazel, 1997

P-515

515

*

*

~494

*

Mycetophyllia sp.

Fux and Mazel, unpublished

P-515

515

*

*

505

*

Montastraea annularis

Mazel, 1997; Manica & Carter, 2000

P-515

515±3

*

*

505±3

*

Montastraea cavernosa (mc2/3/4)

Kelmanson & Matz, 2003

P-515

515

*

*

*

*

Lobophyllia hemprichii (red)

Salih et al., 2004

P-515

515

*

*

*

*

Colpophyllia natans

Fux and Mazel, unpublished

P-515

515

*

*

*

*

Scolymia sp.

Mazel, 1997

P-515

515

*

*

*

*

Plesiastrea verispora (green morph)

Gilmore et al., 2003

P-515

515

*

*

*

*

Plesiastrea verispora (green morph)

Salih et al., 2004

P-515

515

*

*

*

*

Agaricia sp.

Mazel, 1995

P-515

515

*

*

*

*

Ricordea sp.

Mazel, 1995

P-516

516

*

*

486

*

Pocillopora damicornis

Salih et al., 2000

P-516

516

*

*

506

~480

Montastraea cavernosa (=mc2/3/4 - see P-515)

Labas et al., 2002

P-516

516

*

*

*

*

Lobophyllia hemprichii

Nienhaus et al., 2005

P-517

517

555

485

505

465

Acropora tenuis

Papina et al., 2002

P-517

517

574

*

506

566

Ricordea florida

Labas et al., 2002

P-517

517

*

*

506

*

Ricordea florida

Mazel, 1995

P-517

517

*

*

507

*

Favia favus

Tsutsui et al., 2005

P-517

517

551

483

*

*

Montastraea annularis

Mazel, 1995

P-518

518

*

*

508

475

Ricordea florida

Labas et al., 2002

P-518

518

*

*

*

*

Acropora cytheria @ Waikiki Aquarium

Hochberg et al., 2004

P-518

518

*

*

*

*

Acropora digitifera

Hochberg et al., 2004

P-518

518

*

*

*

*

Plesiastrea verispora (green morph)

Salih et al., 2004

P-518

518

*

*

*

*

Montastraea cavernosa

Kelmanson & Matz, 2003

P-518

518

*

*

503

*

Family Pectiniidae

Ando et al., 2004

P-518

518

*

*

*

*

Ricordea florida

Mazel, 1995

P-519

519

*

*

~505

*

Montastraea cavernosa

Kelmanson & Matz, 2003

P-519

519

*

*

*

*

Lobophyllia hemprichii (red)

Salih et al., 2004

P-519-557

519-557

590

*

*

*

Madracis carmabi

Vermeij et al., 2002

P-519-559

519-559

590

*

*

*

Madracis senaria

Vermeij et al., 2002

P-519-570

519-570

590-615

*

*

*

Madracis pharensis (green tissue)

Vermeij et al., 2002

P-520

520

*

*

*

*

Ricordea florida

Mazel, 1995

P-520

520

*

*

488

*

Goniopora tenuidens

Salih et al., 1999

P-520-555

520-555

590

*

*

*

Madracis carmabi

Vermeij et al., 2002

P-520-558

520-558

590

*

*

*

Madracis senaria

Vermeij et al., 2002

520-570

520-570

590

*

*

*

Madracis pharensis (green tissue @ 10m)

Vermeij et al., 2002

520-570

520-570

590

*

*

*

Madracis pharensis (green tissue @ 20m)

Vermeij et al., 2002

520-570

520-570

590-620

*

*

*

Madracis pharensis (green tissue @ 40m)

Vermeij et al., 2002

520-570

520-570

590

*

*

*

Madracis pharensis (green tissue @ 60m)

Vermeij et al., 2002

P-522

522

*

*

499

**

Anemonia sculata var. rufescens

Wiedenmann et al., 2000

P-522

522

*

*

*

*

Montastraea cavernosa

Kelmanson & Matz, 2003

P-522-623

522-623

*

*

*

*

Madracis formosa @ 40m

Vermeij et al., 2002

P-530

530

*

*

450

**

Porites astreoides

Mazel, 2003

P-532

532

590

*

*

*

Madracis pharensis (brown tissue @ 10m)

Vermeij et al., 2002

P-532

532

*

*

*

*

Madracis pharensis (red tissue @ 10m)

Vermeij et al., 2002

P-533

533

590

*

*

*

Madracis pharensis (brown tissue @ 20m)

Vermeij et al., 2002

P-534

534

575

*

*

*

Madracis formosa @ 60m

Vermeij et al., 2002

P-534

534

593

*

*

*

Montastraea cavernosa @ 60m

Vermeij et al., 2002

P-535

535

587

*

*

*

Madracis pharensis (brown tissue @ 60m)

Vermeij et al., 2002

P-537

537

590

*

*

*

Madracis pharensis (grey and blue tissue @
10m)

Vermeij et al., 2002

P-538

538

~580

*

528

494

Zoanthus 2

Matz et al., 1999

P-538

538

*

*

525

494

Zoanthus sp.

Yanushevich et al., 2002

P-540

540

*

*

*

*

Plesiastrea verispora (blue morph)

Salih et al., 2004

P-540

540

*

*

*

*

Plesiastrea verispora (green morph)

Salih et al., 2004

P-542

542

*

*

*

*

Agaricia undata @ 40m

Vermeij et al., 2002

P-550

550

*

*

530

*

Porites murrayensis

Dove et al., 2001

P-557

557

600

545

*

*

Agaricia sp.

Mazel, 1995

P-559

559

590

*

*

*

Madracis senaria @ 60m

Vermeij et al., 2002

P-560

560

590

*

*

*

Madracis pharensis @ 10m (grey tentacles)

Vermeij et al., 2002

P-561

561

*

*

548

*

Fungia concinna

Karasawa et al., 2004

P-561

561

587-616

*

*

*

Madracis senaria @ 40m

Vermeij et al., 2002

CP-562

*

*

*

562

*

Anemonia sulcata, immature P-595

Wiedenmann et al., 2002

P-565

565

*

*

490

*

Agaricia humilis

Mazel et al., 2003

P-565

565

*

*

548

*

Cerianthus sp.

Ip et al., 2004

P-573

573

510

*

*

*

Ricordea florida

Mazel, 1995

P-574

574

517

*

506

566

Ricordea florida

Labas et al., 2002

P-574

574

550

*

*

*

Plesiastrea verispora

Dove et al., 2001

P-575

575

~630

*

~525

~570

Montastraea cavernosa

Mazel, 1997

P-575

575

*

*

506

555

Montipora (digitata/angulata)

Mazel, unpublished

P-575

575

*

*

557

*

Dendronephthya

Pakhomov et al., 2004

P-575

575

630

*

520

*

Scolymia sp.

Mazel et al., 2003

P-575

575

*

*

~569

~540

Phycoerythrin within symbiotic cyanobacteria in
coral

Mazel et al., 2004

Comments about
Green Fluorescent Proteins

It seems quite clear that GFPs emissions are quite varied
and abundant in coral reef animals. At least some GFPs require
the presence of oxygen for maturation – the transition
from a colorless state to one of fluorescence with the emission
peaking in the green portion of the spectrum, yet once mature,
oxygen apparently has no further effect (Tsien, 1998).
However, modification of environment can cause further
color-shifting, resulting in various apparent colorations
(Labas, 2002).

Fluorescent Coloration is Not Produced by
Zooxanthellae! This is one of the persistent myths
within the hobby yet there is no data to support this
view. To the contrary, the evidence does support
fluorescent pigment production by the host. Kawaguti
(1966) shows several electron photomicrographs of pigment
granules apparently being produced by a coral cell’s
endoplasmic reticulum. With that said, zooxanthellae
pigmentation (photopigments including chlorophyll a,
c², peridinin and perhaps others) can greatly
influence the non-fluorescent coloration ranging from brown to
yellow-green.

Possible
Functions of GFP-like Compounds

Opinions on possible function (or non-function) of
fluorescent proteins are almost as numerous as the number of
papers addressing the subject. Here are a few:

Photoprotection? Perhaps the most popular concept is
one where pigments act as sunscreens – photoprotectants
– against ultraviolet or visible radiation. Fairly early
on in the course of ‘serious’ coral reef studies,
Kawaguti (1944) was of the opinion that fluorescent pigments in
corals act to shield symbiotic zooxanthellae from ‘strong
sunlight.’ His idea became mantra for decades and
sporadic re-visitations seemed to confirm his thoughts (see
Salih et al., 1998; Salih et al., 2000 and others).

Fluorescent pigments can cause a reflection of light, which
can be 40-80% higher than that of adjacent
non-fluorescent cells (Salih et al., 1998), leading to the
conclusion that polyp retraction can produce a highly
reflective layer of varying optical density thereby protecting
gonads and high-growth areas (polyp tips,
‘anchoring’ basal tissues).

A Photosynthetic Aid? Schlichter et al. (1985) were
perhaps the first to describe fluorescence as a potential aid
to photosynthesis. These researchers documented
behavior of fluorescent granules and dispersed pigmentation in
the deep-water coral Leptoseris fragilis (found at
depths of 100-145m, or ~325-475’ at Eilat, Israel on the
Red Sea). Normally, this coral appears dark brown since its
chromatophores (pigment-containing granules) are beneath a
layer of symbiotic zooxanthellae. However, the color changes
from to green in less than 1 minute after coral is transferred
to daylight conditions. It is thought that host tissue
contractions could force zooxanthellae downwards, or move
chromatophores upwards through displacement, possibly via a
vascular microtubule system within the coral’s tissue.
Schlichter states that violet light is absorbed by the host
pigment and is fluoresced as bluish-green light that is usable
in photosynthesis. These deep-water corals receive only up to
10 µmol·m²·s PAR at noon and would need to
efficiently collect light – much radiation making it
through a densely packed zooxanthellae layer above the
fluorescent pigment could be absorbed and fluoresced in an
altered wavelength. Though the paper does not state as much, it
could be that fluorescence shifts absorbed wavelengths to a
bandwidth normally rarified at this depth thus avoiding
photosaturation at those wavelengths usually transmitted
through the water column. See Figure 36.

In a later paper, Schlichter et al. (1986) further discuss
that pigment granules (chromatophores) fluoresce reddish while
the intense turquoise autofluorescence seems dispersed
throughout the cytoplasm, and is not in any specialized
structure. Interestingly, we could speculate that the red
fluorescence is also of benefit to
photosynthesis.

Figure 36. The colored lines
represent excitation and emission – the excitation being
the initial peak. Fluorescence is noted at excitation
wavelengths of 380, 390 and 400 nm. Little fluorescence is
noted when the pigment(s) is exposed to bandwidths peaking at
430 and 510nm. After Schlichter et al., 1986.

Phototaxis: A Beacon for Zooxanthellae? This
rather interesting concept involves phototaxis (a movement of
an animal or plant towards light) and was proposed by
Hollinsworth et al. in 2005. Cultured motile
(non-symbiotic) zooxanthellae were exposed to white light which
was split into a spectrum and projected on the culture flask.
The idea was to determine if these dinoflagellates had a
preference for any particular ‘color.’ Apparently
they did – they swarmed in the area illuminated by green
light. Blue light attracted significantly fewer zooxanthellae.
Interestingly, previous observations suggested the motile
zooxanthellae would move out of the area irradiated with
ultraviolet wavelengths. These observations prompted a
hypothesis – green fluorescence may act as a beacon,
attracting free-swimming zooxanthellae to coral recruits or
planulae. Of course, other factors are undoubtedly in involved
with corals attracting symbionts – corals are known to
release chemical cues to the environment and it has been proven
that zooxanthellae can swim against weak currents to reach a
host (Pasternak et al., 2006). If we were to mesh these
observations, we might arrive at the hypothesis that chemical
cues released by the coral act as a navigational beacon to
potential symbionts while green fluorescence is akin to landing
strip lights.

GFP: A Shading Function for Photoreceptors?
This thought was advanced in a paper by Shagin et al.
(2004) and briefly discussed the possibility that GFP might
shield the photoreceptors of the jellyfish Aequorea
victoria. In addition, Burr et al. (2000) advanced the
possibility of a protein (hemoglobin) in a nematode as possibly
possessing an optical function. (Hemoglobin concentrates
densely around Mermisnigrescens’
photoreceptor and is thought to play a role in
phototaxis.) Some coral species have photoreceptors as
well (Gorbunov and Falkowski, 2002), but to my knowledge no one
has advanced a hypothesis linking fluorescence and protection
of coral photoreceptors via optical shading. However a
shielding function by GFP has been suggested for the
non-photosynthetic soft coral Carijoariisei
(Khang and Salih, 2005).

This ends our discussion of potential functions of GFPs, and
we will now turn our attention to specific green fluorescent
proteins beginning with P-512.

Green-Blue
Pigments

P-512

Host: Discosoma, Pigment 3

Excitation: 503nm

Emission: 512nm

Stokes shift: 9nm

Reference: Labas et al., 2002

Comments: P-512 is one of several identified in the Discosoma genus.
See Figure 37.

Figure 38. Note that the
chart’s line represents the emission spectrum. The
absorption curve probably resembles that in Figure 37. After
Mazel, 1995.

P-514

Host: Acropora aspera

Excitation: 501nm, shoulder at 480nm

Emission: 514nm, shoulder at 490nm

Stokes shift: 13nm

Reference: Papina et al., 2002

Comments: Collected off the coast of Okinawa, Japan in 1.5m
of water, in August of 2001. This Acropora specimen
appeared yellow-green in natural light and fluoresced
bluish-purple when excited with UV-A radiation peaking at
365nm. Shifts in pH (5.0-8.0) do not significantly affect
excitation and emission wavelengths or fluorescent quantum
yield. See Figure 39.

Host: Montastraea cavernosa

Excitation: ~505nm

Emission: 514nm

Stokes shift: ~9nm

Reference: Kelmanson and Matz, 2003

Comments: Found in a red M. cavernosa specimen
collected in the Florida Keys National Marine
Sanctuary.

Host: Entacmaea quadricolor (Actinaria)

Excitation: N/A

Emission: 514nm

Stokes shift: N/A

Reference: Wiedenmann et al., 2002

Comments: Precursor to P-611. The fluorescence is stable
over a pH range of 4-10.

Figure 39. More than a few
hobbyists have seen this particular fluorescent pigment. After
Papina et al., 2002.

P-515

P-515’s fluorescence can contribute significantly to
daylight appearance and is often found in conjunction with
other fluorescent pigments (Fux and Mazel, 1999).

Host: Mycetophyllia lamarckiana

Excitation: ~500-505nm

Emission: 515nm

Stokes shift: 10-15nm

Reference: Mazel, 1997

Comments: See Figure 40.

Host: Montastraea annularis

Excitation: Not listed

Emission: 515nm

Stokes shift: N/A

Reference: Mazel, 1997

Host: Montastraea sp.

Excitation: Not listed

Emission: 515nm

Stokes shift: N/A

Reference: Fux and Mazel, unpublished

Host: Montastraea cavernosa

Excitation: 505±3

Emission: 515±3nm

Stokes shift: ~10nm

Reference: Kelmanson and Matz, 2003.

Comments: M. cavernosa can contain a number of
pigments. There are several with similar emissions, and are
referred to as P-515±3 by Kelmanson and Matz. See Figure 41.

Host: Scolymia sp.

Excitation: Not listed

Emission: 515nm

Stokes shift: N/A

Reference: Fux and Mazel, unpublished

Host: Mycetophyllia sp.

Excitation: Not listed

Emission: 515nm

Stokes shift: N/A

Reference: Fux and Mazel, unpublished

Host: Colpophyllia sp.

Excitation: Not listed

Emission: 515nm

Stokes shift: N/A

Reference: Fux and Mazel, unpublished

Host: Plesiastrea verispora

Excitation: Not listed

Emission: 515nm

Stokes shift: N/A

Reference: Gilmore et al., 2003.

Comments: These Plesiastrea specimens (appearing blue
in natural light due to a non-fluorescent chromoprotein) were
collected in 5-9m of water at Port Jackson,
Australia.

Figure 40. Excitation and emission
wavelengths of a pigment found in the stony coral
Mycetophyllia. After Mazel, 1997.

Figure 41. The spectral signature
of this pigment is very similar to a number of pigments found
with stony corals Montastraea. After Kelmanson and Matz,
2003.

P-516: Precursor of Pigment
581

Host: Montastrea cavernosa

Comments: Relative brightness of this green form is 1.28
(when compared to a modified form of A. victoria GFP).

Host: Pocillopora damicornis

Excitation: 486nm

Emission: 516nm

Stokes shift: 30nm

Reference: Salih et al., 2000.

Host: Lobophyllia hemprichii

Excitation: ~510nm

Emission: 516nm

Stokes shift: 6nm

Reference: Nienhaus et al., 2005

Comments: These researchers observed this green form
(emission peak at 516nm) maturing to red fluorescence (peak at
581nm) when irradiated with ‘blue’ light (actually
violet) at ~400nm. This maturation is driven by light energy
and not chemical oxidation. See Figure 43 for
excitation/emission spectra.

Host: Montastraea annularis

Host: Acropora tenuis

Excitation: 505nm, shoulder at 465nm.

Emission: 517nm, 555nm and 485nm.

Stokes shift: 12nm

Reference: Papina et al., 2002

Comments: This A. tenuis specimen was collected in
August 2001 at a depth of 1.5m in Okinawa, Japan. It appeared
to the observer as brown in natural light, and fluoresced green
under a black light. Spectral chart is that of an intact coral.
Papina et al. noted no significant shifts of either fluorescent
quantum yield or spectral characteristics over a pH range of
5.0 to 8.0. See Figure 44.

P-517 variant: Precursor of
Pigment 593

Host: Favia favus

Comments: Pigment 517 from Favia favus is
photoconvertible to P-593 (green to red). Relative brightness (compared
to an engineered GFP from
Aequorea victoria) is 1.12. See Figure 45.

Figure 45. The spectra of a GFP
from a stony coral in its immature state. The mature form is
red with a peak emission at 593nm. After Tsutsui et al.,
2005.

Pigment 517 variant: Precursor to
Pigment 574

Host: Ricordea florida

Excitation: 506nm

Emission: 517nm

Stokes shift: 11nm

Reference: Labas et al., 2002

Comments: See Figure 46.

Figure 46. If we are to believe
the thoughts of some researchers, this
‘double-peaked’ spectrum is indicative of a pigment
in transition from green to red. This pigment was isolated from
Ricordea florida. After Labas et al., 2002.

Host: Acroporadigitifera

Comments: Found in an Acropora digitifera specimen on
a shallow reef flat (depth of 0.1m; ~4”), Mayoette,
Comorros.

Host: Family Pectiniidae

Excitation: 503nm

Emission: 518nm

Stokes shift: 15nm

Reference: Ando et al., 2004

Comments: This is an interesting protein – its
fluorescence is ‘switchable.’ The green pigment is
bleached upon exposure to intense light at ~490nm. The green
fluorescence returns upon exposure to violet light at about
400nm. This photoconvertible pigment (from green fluorescence
to non-fluorescent) is commercially available as
“Dronpa” (“Dron” being a ninja term for
‘vanishing’ and ‘pa’ for
photoactivatible) and was isolated from a coral in the family
‘Pectiniidae’ (which includes genera Echinophyllia, Oxypora, Mycedium and Pectinia – Veron,
1986). Relative brightness of this green form is 2.40 (when compared
to a modified form of A. victoria GFP).

Host: Ricordea florida

Excitation: 508nm

Emission: 518nm

Stokes shift: 10nm

Reference: Labas et al., 2002

Host: Montastraea cavernosa

Excitation: ~505nm

Emission: 518nm

Stokes shift: ~13nm

Reference: Kelmanson and Matz, 2003

Comments: This pigment was found in a green fluorescent M. cavernosa collected
in the Florida Keys.

Figure 47. Spectral signatures of
P-518 isolated from Ricordea florida by Labas et al.,
2002. The excitation and emission spectra are identical to that
of P-518 described in Montastraea cavernosa by Kelmanson and
Matz (2003).

P-518 could also be an immature green form of the red
fluorescent protein Kaede (P-582), although it is difficult to
believe the pigment would not mature in shallow water as
described by Hochberg et al., 2004. This could simply be a
non-photoconvertible form of P-518.

P-519

Host: Montastraea cavernosa

Excitation: Not listed

Emission: 519nm

Stokes shift: N/A

Reference: Kelmanson and Matz, 2003

Comments: Pigment 519 was found in a red fluorescent M.
cavernosa collected in the Florida Keys. No excitation
wavelength is listed; however, its emission spectrum is almost
identical to P-518.

P-520: Precursor of Pigment
580.

Host: Ricordea florida

Excitation: Not listed

Emission: 520nm

Stokes shift: N/A

Reference: Mazel, 1995.

Comments: This pigment might be the immature form of the
‘red’ fluorescent P-580. See below.

Host: Montastraea cavernosa

Excitation: 508nm, with a shoulder at 572nm

Emission: 520nm, with shoulder at 580nm

Stokes shift: 12nm and 8nm

Reference: Labas et al., 2002.

Comments: Possibly the same pigment found in Ricordea
florida by Mazel (1995)?

P-520: Precursor of Pigment
611.

Host: Entacmaea quadricolor

Excitation: ~500nm

Emission: ~520nm

Stokes shift: 20nm

Reference: Nienhaus et al., 2003.

P-522

Host: Montastraea cavernosa

Excitation: Not listed

Emission: 522nm

Stokes shift: N/A

Reference: Kelmanson and Matz, 2003.

Comments: This pigment was found in a red Montastraea
cavernosa collected in the Florida Keys National Marine
Sanctuary.

Host: Anemonia sculata

Excitation: 511nm

Emission: 522nm

Stokes shift: 11nm

Reference: Wiedenmann et al., 2000

Comments: Note the double-peaked emission in Figure
48.

Figure 48. The excitation and
emission suggest photoconversion is possible in this pigment.
After Wiedenmann et al., 2000.

P-530

Host: Porites astreoides

Excitation: ~500nm

Emission: 530nm

Stokes shift: ~30nm

Reference: Mazel et al., 2003

Comments: See Figure 49 for excitation and emission
spectra.

Figure 49. Spectral qualities of a
pigment found in the Caribbean coral Porites astreoides.
After Mazel et al., 2003.

Yellow-Green
Pigments

P-538

Host: Zoanthus 2.

Excitation: 528nm

Emission: 494nm and 538nm

Stokes shift: 10nm

Reference: Matz et al., 1999; Labas et al., 2002

Comments: P-538 was isolated by Matz et al. (1999)
from a Zoanthus species and found in combination with
another fluorescent pigment (P-506). Fluorescent
Quantum Yield and Relative Brightness are fairly low –
0.42 and 0.38, respectively. See data of Yanushevich et al.
(2002) in Figure
50.

Figure 51. Compare the spectral
qualities of this pigment to that in Figure 50 – they are
almost identical. After Matz et al.,
1999.

P-550

Host: Porites murrayensis

Excitation: 530nm

Emission: 550nm

Stokes shift: 20nm

Reference: Dove et al., 2001

Comments: This coral was purple when viewed in natural light
due to the presence of a non-fluorescent protein. Maximum host
tissue/zooxanthellae absorbance is at 576nm (data not
shown).

P-557

Host: Agaricia sp.

Excitation: Not listed

Emission: 557nm

Stokes shift: N/A

Reference: Mazel, 1995

Comments: Emission also has shoulders at 600nm and 545nm.
Reports of this particular pigment are practically
non-existent, with Mazel’s reports being the only ones of
which I am aware. See Figure 52. (Mazel reports yellow Agaricia are
common in Bonaire - personal communication).

Figure 52. A rather unique
yellowish fluorescent protein found it in the Caribbean stony
coral Agaricia. After Mazel, 1995.

P-561 (Kusabira-Orange)

Host: Fungia concinna

Excitation: 548nm

Emission: 565nm

Stokes shift: 17nm

Reference: Karasawa et al., 2004.

Comments: Commercially available from MBL International
under the trade name “Kusabira-Orange”. Wild type
P-561 has a fluorescent quantum yield of 0.45, and is not pH
sensitive (pKa <5.0). The Japanese name for Fungia is
“Kusabira-ishi.”
See Figure 53.

Figure 53. A true orange
fluorescent protein found in the popular ‘mushroom’
stony coral (Fungia). After Karasawa et al., 2004.

P-562 (or asCP-562)

Host: Anemonia sculata

Excitation: 559nm

Emission: 562nm (immature form)

Stokes shift: 52nm

Reference: Wiedenmann et al., 2002

Comments: This yellow green pigment is found in the anemone
(Anemonia sculata) and is technically fluorescent
although laboratory instruments are needed to detect it. Under
certain conditions, this pigment can transform from
yellow-green to red with a very weak emission maximum at
611nm.

P-565

Host: Agaricia humilis

Excitation: 490nm

Emission: 565nm

Stokes shift: 75nm

Reference: Mazel et al., 2003.

Comments: See Figure 53.

Host: Cerianthus sp.

Excitation: 548nm

Emission: 565nm

Stokes shift: 17nm

Reference: Ip et al., 2004.

Comments: This pigment is apparently spectrally different
from the P-565 found in Agaricia stony corals.

An Early GFP Description

In homage to Siro Kawaguti, one of the first researchers of
coral coloration, Table 3 describes some of the properties of
fluorescent pigments found in Pacific corals. Though much of
Kawaguti’s early works were completed and published in
the late 1930’s and 40’s, his ideas, for the most
part, have withstood the test of time. His equipment was not as
sophisticated as that of today and did not offer great
precision, yet his descriptions are remarkable. His works offer
perspectives on GFPs and the varieties of coral hosts and
complement later research. Note that his work deals with mostly
emission wavelengths (as seen in the ‘1st
Band’ and ‘2nd Band’ columns)
while absorbance (‘Max. Abs. 1’ and ‘2’
columns is rarely described. See Table
5.